Although the immune response is often seen as beneficial, in certain circumstances the immune response to an antigen can actually be harmful to the animal in which the immune response occurs. An example where the immune response creates a condition wherein the host is subject to serious pathologic sequelae is in such autoimmune diseases as lupus erythematosus. In lupus erythematosus, antibodies are often present which react with determinants in the thyroid, erythrocytes, DNA, and platelets of the host.
Another example of where the suppression from immune response would be described is in the treatment of allergies. It has been established that IgE antibodies against allergens cause hay fever, and are involved in the other allergic diseases such as extrinsic asthma. The crucial role of IgE antibodies in the allergic diseases raised the possibility that the regulation and suppression of the IgE antibody formation against allergens would be one of the fundamental treatments for allergic diseases. For example, in the serum of hay fever patients sensitive to ragweed allergens, IgE antibodies against the allergens are always detected. The IgE antibody titer goes up after the pollen season, and then declines only slightly during the rest of the year. Since the half life of IgE in the serum is only 2 to 3 days, the persistence of the IgE antibody titer indicates that the antibodies are being synthesized continuously by the lymphoid cells of the patients in spite of the lack of allergen exposure.
Over the past 20 years, several different attempts were made to control the IgE antibody response in experimental animals. One of the approaches was to improve classical immunotherapy or desensitization treatment, in which allergic patients receive repeated injections of a minute dose of allergen. It was shown that the desensitization treatment can improve clinical symptoms in some patients. However, the IgE antibody titer in the serum of hay fever patients did not decline after the treatment. The major immunological effects of the treatment is an enhancement of the IgG antibody formation, and the suppression of an increase in the IgE antibody titer after the pollen season.
A limitation in the desensitization, or immunosuppression treatment is that patients cannot tolerate a large dose of allergen because of side effects. In order to overcome this difficulty, attempts were made to use a chemically modified allergen, such as urea-denatured antigen or polyethylene glycol (PEG)-conjugates of the antigen for the treatment. Since the modified antigens do not bind to antibodies against the native antigen, relatively large doses of the modified antigen can be injected without causing allergic symptoms. However, the modified antigen can stimulate antigen-specific T-cells. Evidence was obtained that intravenous injections of the modified antigen into mice resulted in the generation of antigen-specific suppressor T-cells which suppressed the primary IgE antibody response to the native antigen. However, the treatment had minimal effects on the on-going IgE antibody formation, if the treatment were initiated after the antibody titer reached maximum (Takatsu and Ishizaka, J. Immunol., 117: 1211, 1976). In agreement with the observations in the mouse, clinical trials of polyethylene-glycol-conjugated allergen in hay fever patients showed that the treatment failed to diminish the IgE antibody titer. Failure of the repeated injections of the modified antigen to suppress the on-going IgE antibody formation is probably due to the presence of a relatively large population of antigen-specific helper T-cells in the allergic patients. Since the modified antigen not only induces the generation of antigen-specific suppressor T-cells, but also expands the population of helper T-cells, this latter effect of the treatment might have overcome the effect of suppressor T-cells. This interpretation is supported by the fact that transfer of antigen-specific suppressor T-cells into immunized mite resulted in the suppression of the on-going IgE antibody formation (Takatsu and Ishizaka, J. Immunol, 117: 1211, 1976). The results collectively suggested that the persistent IgE antibody formation in hay fever patients could be suppressed, if it were possible to generate the antigen-specific suppressor T-cells without expanding the helper T-cell populations.
Since 1980, the inventors have investigated various ways in which IgE synthesis is selectively regulated in an immunoglobulin isotype-specific manner. As a result of this research, two types of T-cell factors have been found which have affinity for IgE and selectively regulate IgE synthesis. One of the IgE-binding factors (IgE-BF) selectively enhances the IgE response, while the other type of IgE-BF selectively suppresses the response. The major difference between the IgE-potentiating factors and IgE-suppressive factors appears to be carbohydrate moieties in the molecules. The IgE-potentiating factors bind to lentil lectin and concanavalin A, while IgE-suppressive factors fail to bind to these lectins (Yodoi, et al., J. Immunol., 128: 289, 1982). Analysis of the cellular mechanism for the selective formation of either IgE-potentiating factors or IgE-suppressive factors, as well as gene cloning of the factors, indicated that the IgE-potentiating factor and IgE-suppressive factor share a common structural gene and that the nature of the carbohydrate moieties and biologic activities of the factors are established during the post-translational glycosylation process (Martens, et al, Proc. Nat'l Acad. Sci., U.S.A., 84: 809, 1987). Under the physiological conditions, this glycosylation process is controlled by two T-cell factors which either enhance or inhibit this process. These factors are denominated glycosylation inhibiting factor (GIF) and glycosylation enhancing factor (GEF).
A unique property of GIF is its biochemical activity. This lymphokine binds to monoclonal antibodies against lipomodulin (a phospholipase inhibitory protein) and appears to be a phosphorylated derivative of a phospholipase inhibitory protein (Uede, et al., J. Immunol., 130: 878, 1983). It was also found in the mouse that the major source of GIF is antigen-specific suppressor T-cells (Ts) (Jardieu, et al., J. Immunol., 133: 3266, 1984). Subsequent experiments on ovalbumin (OVA)-specific suppressor T-cell hybridomas indicated that stimulation of the hybridoma cells with antigen (OVA)-pulsed syngeneic macrophages resulted in the formation of GIF that has affinity for OVA (antigen-binding GIF). However, the same hybridomas constitutively secreted GIF having no affinity for OVA (nonspecific GIF). Studies on the relationship between nonspecific GIF and OVA-binding GIF indicated that the antigen-binding GIF is composed of an antigen-binding polypeptide chain and a nonspecific GIF (Jardieu, and Ishizaka, in Immune Regulation By Characterized Polypeptides, Goldstein, et al., eds., Alan R. Liss, Inc., N.Y., p595, 1987). It was also found that the antigen-binding GIF shares common antigenic determinants with antigen-specific suppressor T-cell factors (TsF) described by the other investigators, and suppressed the antibody response in an antigen (carrier)-specific manner. Furthermore, not only antigen-binding GIF, but also antigen-specific TsF described by other investigators, bound to immunosorbent coupled with monoclonal anti-lipomodulin (141-B9), and were recovered by elution of the immunosorbent at acid pH.
Despite the major limitations of desensitization in treating allergy, this technique continues to be the method of choice. Consequently, there is significant need for a technique which is antigen-specific yet does not have associated with it the side effects seen with existing desensitization regimens.
The suppression of the immune response is crucial in order to prevent host versus graft (HVG) and graft versus host rejection (GVH). Unfortunately, in the case of both autoimmune disease as well as in HVG and GVH, the immune response suppression uses highly toxic drugs which are of limited effectiveness and act systemically, rather than specifically. The severe limitations of such therapy point to the need for immunosuppressive agents which have less toxicity, but greater specificity.
An improved way to suppress an immune response to an antigen in a human would be to administer an immunosuppressively effective amount of human GIF which can specifically bind to the antigen. In so doing, the concentration of T suppressor factor is favored and, as a result, the immune response to the antigen is decreased. The present invention provides a means for accomplishing this result.